JPH0214665B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention particularly relates to an ultrasonic transmitting/receiving device that can obtain clear tomographic images with high resolution in ultrasonic diagnosis and the like.

BACKGROUND ART In the fields of medical diagnosis, metal flaw detection, and the like, a method is widely used in which the interior of a subject is electronically scanned using ultrasonic waves, and the reflected waves are received and analyzed to obtain a tomographic image of the subject. In this case, in order to increase the lateral resolution, a method is used in which the ultrasonic waves are scanned while being electronically controlled so that they are focused at a certain depth inside the subject. The focusing method is to drive each of the piezoelectric transducers arranged in an array with a predetermined phase difference, as in the case of general sector scanning.

In a tomographic image produced by such a focused scanning method, only the area very close to the position (focal point) where the ultrasonic waves are focused is particularly clearly imaged, but the other areas remain unclear. Another way to clearly see the diagnostic area is to provide a special knob for changing the focus, and by turning this knob, the focus is moved to the diagnostic area.
It has not yet been possible to meet the requirement of displaying the entire screen clearly.

An object of the present invention is to provide an ultrasonic transmitter/receiver type that can obtain clearer images over the entire screen.

The present invention provides an ultrasound transmitting/receiving device that electronically focuses and transmits ultrasound waves to a predetermined location within a subject and receives reflected waves from inside the subject.
means for successively transmitting ultrasonic waves of a plurality of different frequencies corresponding to a plurality of focusing areas on one scanning line in order from a focusing area farthest from a sending point during a period of scanning one scanning line; It is characterized by comprising a gate that allows reflected waves from the region to pass in order from a convergence region closest to the transmission point, and a filtering means that filters waves corresponding to the plurality of frequencies.

The apparatus of the present invention will be explained below with reference to Examples.

FIG. 1 is a diagram for explaining an example in which the apparatus of the present invention is applied to a sector electronic scanning method. Ultrasonic waves are sequentially transmitted from an ultrasonic transducer 10 in which piezoelectric transducers are arranged in an array toward the inside of the subject in N directions d1 to dN, which are the same as the number of scanning lines of a display device, for example, a cathode ray tube. Ru. In this case, on one scanning line, for example, the scanning line in direction dn,
First, an ultrasonic wave v1 whose focus is at the intersection with the arc c1 is sent out, and then ultrasonic waves v2 to v5 whose focus is at the intersections with the arcs c2 to c5 are sequentially sent out. ultrasound v1
The ultrasonic waves are transmitted at almost the same time that the ultrasonic waves or v5 reach their respective focal points, and the last ultrasonic wave
From the time when v5 was sent out, the same ultrasonic transducer 1
Reception starts with 0. First, ultrasonic transducer 1
0 receives the reflected wave from the ultrasonic wave v5 reflected in the section from the base point 0 to the arc c5, then the ultrasonic wave v4 receives the reflected wave reflected in the section from the arc c5 to the arc c4, and so on. The reception timing and the time width of the gate are set so that the reflected waves reflected in the sections between the respective arcs are sequentially received up to the ultrasonic wave v1.
After the reception is completed, scanning is performed to the next scanning line dn+1.

FIG. 2 is a diagram for explaining an example in which the apparatus of the present invention is applied to a linear electronic scanning system. An ultrasonic transducer 10 having a relatively large number of piezoelectric transducers is used, and a plurality of piezoelectric transducers in the vicinity of one scanning line are selected and driven with a predetermined phase difference. As is clear from a comparison with FIG. 1, the only difference is whether the scanning lines are fan-shaped or parallel, and the timing of transmitting and receiving ultrasonic waves is exactly the same as that explained in FIG.

FIG. 3 shows a time chart of transmission and reception of ultrasonic waves in the embodiment of the present invention explained in FIGS. 1 and 2. The horizontal axis is the time axis, and the vertical axis represents the waveforms of the transmitted ultrasonic waves v1 to v5 and the operation waveforms of the receiving gates G1 to G5.

Transmission and reception are performed from time t1 to time t12 on one scanning line. That is, five ultrasonic waves v1 to v5 are transmitted between time t1 and time t5, and at time t5
5 gates G1 to G during time t11
Each reflected wave is received by 5. Since receiving requires time for pulses to travel back and forth, the opening time width of each gate is set to twice the sending pulse interval. If a strong reflected wave immediately after the ultrasonic wave is not required, the gate G1 for receiving the fifth ultrasonic wave v5 may be opened at time t6, which is delayed from time t5. The reflected waves of the ultrasonic waves v5 and v1 received by the gates G1 and G5 are each corrected according to the distance to the reflection point, converted into a video signal, and displayed on one scanning line (raster) of the display device. Displayed in sequence. At time _t12 , the next scanning line is entered and similar transmission and reception are repeated.

In the above example, a method was shown in which five ultrasonic waves with five different focuses are sent out on one scanning line, and five clear areas are displayed on the screen. It becomes clear. However, as ultrasound waves with different foci come closer together, a new problem arises: a decrease in distance resolution due to their superposition. As a method to solve this problem, it is useful to make the oscillation waveform modes of two or more ultrasonic waves that are close enough to overlap and influence each other to be different, and to discriminate based on these modes during reception. . The oscillation waveform modes that should be different include the oscillation frequency and pulse train.

Furthermore, there is a known method for automatically focusing by controlling the phase of each piezoelectric transducer during reception, but this method can be combined with the method of the present invention to achieve automatic focusing for both transmission and reception. Clear images can be obtained.

FIG. 4 is a block diagram showing an embodiment of an apparatus suitable for applying the method of the present invention, which can perform automatic focusing for both transmission and reception, and can discriminate frequencies.

Each piezoelectric transducer of the ultrasonic transducer 10 is connected to a predetermined delay line of a delay circuit 30 via a tap switching circuit 20. The tap switching control information of the tap switching circuit 20 is stored in advance in the storage device 40 so that an appropriate delay amount is given according to the types of ultrasonic waves v1 to v5 having different focal lengths and frequencies in each scanning line, and the tap switching control information is Predetermined storage contents are sequentially selected by the selection circuit 50 in response to a signal a from the device 60, and the taps are switched in accordance with the selected contents.

By the transmission/reception switching signal b from the control device 60,
The transmission/reception switch 70 operates, and switching to the excitation circuit 80 and reception gate circuit 90 is performed. The excitation circuit 80 transmits five types of excitation signals having different frequencies to the delay circuit 30 in response to the signal C from the control device 60, and each excitation signal is sent to the ultrasound transducer 10 after a predetermined delay time. When the transmission of the five types of excitation signals is completed, the transmission/reception switching circuit 70 is switched to the reception side, and the signal received by the ultrasonic transducer 10 is sent again to the reception gate circuit 90 after a predetermined delay time. On the other hand, the control device 60 sends reception gate signals G1 to G5 and sequentially to the reception gate circuit 90 to open a predetermined gate. The signal that has passed through the gate is waved by the wave circuit 100, and only the signal of a desired frequency is sent to the signal processing 110. The signal subjected to predetermined processing by the signal processing circuit 110 is displayed as a video signal on a predetermined scanning line of the display 130 via the display control circuit 120. The operation of each circuit is controlled by the control circuit 60 according to the time chart shown in FIG.

As described above, according to the ultrasound transmitting/receiving device of the present invention, clearer tomographic images can be obtained in ultrasound diagnosis and the like.

[Brief explanation of drawings]

1 to 4 are diagrams for explaining embodiments of the present invention. 10... Ultrasonic transducer, 20... Tap switching circuit, 30... Delay circuit, 40... Storage device, 50
... selection circuit, 60 ... control circuit, 70 ... transmission/reception switching circuit, 80 ... excitation circuit, 90 ... reception gate circuit, 100 ... wave circuit, 110 ... signal processing circuit, 120 ... display control circuit , 130...
display.

Claims (1)

[Claims] 1. In an ultrasonic transceiver that electronically focuses and transmits ultrasound waves to a predetermined location within a subject and receives reflected waves from inside the subject, one scan line is scanned during transmission. means for successively transmitting ultrasonic waves of a plurality of different frequencies corresponding to a plurality of focusing areas on a line, in order from a focusing area farthest from a sending point, and means for transmitting reflected waves from the plurality of focusing areas to 1. An ultrasonic transmitting/receiving device comprising: a gate that passes sequentially from a focusing region; and filtering means that filters waves corresponding to the plurality of frequencies.